Sure, very solvable nowadays with media queries, flex box, grid, screen width and height units, etc. These features didn't exist in 90s CSS.
But even though the tools exist today, it is still challenging to do well. Agreed that aspect ratio variability is a bigger problem (we can no longer count on 4:3 as the standard).
I have a 4K monitor on my desk with 100% scaling, and one of the things that always gives me a chuckle is maximizing a browser window.
Most websites just stop getting wider after a certain point, which is fine because you wouldn't want to read a line of text that long anyway. It's usually a column in the middle maybe 1/3rd of the screen.
But even though the tools exist today, it is still challenging to do well. Agreed that aspect ratio variability is a bigger problem (we can no longer count on 4:3 as the standard).